HOUSTON -- The Houston Police Department's troubled crime lab -- with the exception of its DNA section -- received national accreditation this week.

The lab was accredited by the American Society of Crime Lab Directors in biology except for DNA, toxicology, controlled substances, firearms and document examination.

"Without question, we still have a lot of work to do in terms of getting this lab back up and running to its capacity," said Irma Rios, the crime lab's director. "There is no doubt this national accreditation seal of approval means a lot to the people who have been working tirelessly to regain the public's trust in the work we do."

Public confidence in the lab has been eroded since myriad problems with its work surfaced.

The DNA section was shut down in 2002 when an outside audit found serious deficiencies. The audit cited a lack of training of the lab's employees, insufficient documentation and possible contamination of DNA samples.

Two prison inmates have been released because their convictions were tainted by faulty crime-lab analyses. In 2003, the lab briefly closed its toxicology section after the section's supervisor failed a competency test. Analysis done by the lab's ballistics and serology sections also has been questioned.

Rios said officials hope the lab's DNA section can be accredited by the end of the year.

Inspectors with the American Society of Crime Lab Directors began visiting the lab in September. In February, they told lab officials accreditation would be granted after adjustments were made to the way employees handled records on the custody of evidence.

"I am very proud of the job our employees have done in gaining this noteworthy achievement," said Houston Police Chief Harold Hurtt.

The Legislature has charged the Texas Department of Public Safety with making sure all laboratories in the state are accredited by September.