BOSTON (AP) — A chemist at the center of a drug lab testing scandal admitted she faked results for two to three years, forged signatures and skipped proper procedures, a police report shows. Some of Annie Dookhan's colleagues also had concerns for years about the high number of drug samples she tested and inconsistencies in her work, according to other police reports The Associated Press obtained Wednesday. Lab employees' interviews with investigators show they convinced themselves their concerns were invalid or reported them to supervisors who didn't intervene to stop Dookhan. Dookhan's mishandling of drug samples at the now-closed state lab in Boston has thrown thousands of criminal cases into question, authorities say. A handful of defendants already are free or have had their criminal sentences suspended. Concerns from Dookhan's colleagues prompted two supervisors to audit her work in 2010, but they just looked at paperwork and didn't retest drug samples. Things started to unravel in the spring of 2011, when Dookhan was caught forging a colleague's initials on paperwork after taking 90 drug samples from evidence, according to police. Another colleague told police it was "almost like Dookhan wanted to get caught." Anne Goldbach, forensic services director for the Committee for Public Counsel Services, which oversees the provision of legal representation for indigent people, said the new documents show the problems at the Hinton State Laboratory are more troubling than originally believed. She said it appears there was unsupervised access to the lab's evidence office and evidence safe. While Goldbach said she didn't see evidence of intentional wrongdoing by other chemists, she said that because Dookhan was in charge of quality control equipment other chemists could have gotten false test results without knowing it. "The fact that she failed to conduct quality control steps ... it calls into question all the testing done by the lab," Goldbach said. Attorney John T. Martin, who represents several defendants whose samples Dookhan handled, said he believes she changed drug weights to meet statutory standards for stricter sentencing. Martin said in the cases of four of his clients, Dookhan determined that the weight of the drug sample was just 1 gram above the amount needed for a more serious penalty even though police reports made the seizure seem smaller. Police say Dookhan told them several times in an August interview that she knew she had done wrong. "I screwed up big time," she said while becoming teary-eyed, according to the report by investigators for Attorney General Martha Coakley's office. "I messed up bad. It's my fault. I don't want the lab to get in trouble." Authorities haven't filed charges against Dookhan or commented on her possible motives as their probe continues. Dookhan hasn't responded to repeated requests for comment. In the Aug. 28 interview with two investigators at her dining room table, Dookhan first denied doing anything wrong when she analyzed drug samples. She changed her story after they confronted her with a Boston Police Department retest of a suspected cocaine sample that came back negative after Dookhan identified it as the narcotic. Police also told her the number of samples she reported analyzing was too high and she couldn't have done all the tests. The report shows Dookhan then admitted identifying drug samples by looking at them instead of testing them, called dry labbing. She said she tested about five out of 25 samples she got from evidence, after routinely getting a large number of samples from different cases out of the evidence room, police say. She also told police she contaminated samples a few times to get more work finished but no one asked her to do anything improper, they say. "I intentionally turned a negative sample into a positive a few times," Dookhan said in a signed statement she gave police. Dookhan also told investigators she routinely skirted proper procedures by looking up data for assistant district attorneys who called her directly rather than going through the evidence department. State police say Dookhan tested more than 60,000 drug samples submitted in the cases of about 34,000 defendants during her nine years at the lab. She resigned in March amid an internal investigation by the Department of Public Health. After state police took over the lab in July as part of a state budget directive, they said they discovered her violations were much more extensive than previously believed and went beyond sloppiness into malfeasance and deliberate mishandling of drug samples. In the August police interview, Dookhan said that in June 2011 she improperly took 90 samples that weren't assigned to her from evidence and forged another person's initials on a log book after a supervisor questioned her about it. While Dookhan's lab duties were suspended after that, she said she disobeyed orders and continued to give law enforcement officials information on their cases. Two days after her police interview, Gov. Deval Patrick ordered state police to close the lab. That day, a police lieutenant spoke with Dookhan to tell her she should get an attorney because she could face criminal charges. Dookhan cried on the phone, saying she didn't know any lawyers, didn't have money and was in a long divorce with her husband and didn't want to involve family.