HOUSTON -- The Houston Police Department closed the toxicology section of its troubled crime lab Wednesday after the toxicologist there failed a competency test.

It's the second section of the police lab to be shut since an outside audit 10 months ago revealed significant deficiencies within its DNA section. Crime lab director Irma Rios said the lab has six sections.

"Based on the information, a decision was made to temporarily close the toxicology section of the crime lab and begin an internal affairs investigation," Acting Police Chief Joe Breshears said.

Breshears said Pauline Louie, a 28-year department employee who had supervised the toxicology section for three years, was suspended with pay pending an internal affairs investigation. He declined to detail the duties Louie was found incompetent to perform.

The toxicology section tests blood and urine for alcohol and drugs.

Louie was among the crime lab employees suspended after an internal affairs investigation into the DNA section in June recommended the suspension or firing of nine employees. Louie was suspended for seven days for failing to inspect equipment and complete necessary safety, security and equipment check lists.

"It seems she is a little more unqualified then she has let on," Houston defense attorney Troy McKinney said. "It seems to me that the problem is not with a particular section of Houston Police Department crime lab, it is the entire lab. ... They obviously have structural problems that go well beyond testing."

Harris County District Attorney Chuck Rosenthal said Wednesday Louie's duties included calibrating breathalyzer machines and the police department had not yet checked whether there were any problems with her performance.

If it is determined that Louie failed to perform such duties, McKinney said it could have a much more far-reaching impact than problems found within the lab's DNA section.

Breshears said it was unclear how many cases involving drugs and alcohol that were tested by the toxicology section could be affected.

"I don't believe this problem is anywhere near the problem DNA brought for us," the chief said. "I don't believe there will be near that many cases involved."

Retesting in hundreds of DNA cases has been under way since March after the outside audit revealed serious deficiencies, including a lack of training of the lab's employees, insufficient documentation and possible contamination of DNA samples. A grand jury earlier this month declined to issue any indictments after investigating the DNA section of the lab. The grand jury was critical of the operation.

Breshears called the latest suspension a blow to the lab now, but said he believed the competency testing taking place throughout the lab ultimately would result in improvements overall. He said the lab is working toward becoming accredited by 2005, as required by a new state law passed in September.

"This came to light as a result of our move toward accreditation," Breshears said. "This is unfortunate, but this is part of the growth process we are going to go through as we put the lab back on track again."

Louie had been the only person working in the section and also oversaw lab work in the narcotics section, Breshears said. He said he wasn't aware which sections of the crime lab had job vacancies or if there were openings in Louie's section.

"She was the only person up there so she carried the whole workload," the chief said.

Rosenthal said the situation was frustrating and problematic. He said initial information presented to him was that about 150 cases would need to be reviewed, but said another number had been given to Assistant District Attorney Marie Munier, who has been overseeing retesting of DNA cases.

"It is frustrating there were techniques used over there that weren't correct," Rosenthal said. "This doesn't sound like an abuse. It sounds like an error in technique."

Rosenthal said he was told Louie should have updated the technique she was using in 1999 and failed to do so.

Breshears said most of the 40 to 50 employees within the lab had passed the competency testing, which includes scientific and written tests. He said the competency testing remained under way this week.

"If we do our job right, which we didn't do in the past," he said, "If we move forward as we are supposed to, to meet accreditation standards, we are going to be a better laboratory for it, not a worse one."