WASHINGTON — The Internal Revenue Service has lost more emails connected to the tea party investigation, congressional investigators said Tuesday.

The IRS said last Friday it had lost an untold number of emails when Lois Lerner’s computer crashed in 2011. Lerner used to head the division that handles applications for tax-exempt status.

On Tuesday, two key lawmakers said the IRS has also lost emails from six additional IRS workers whose computers crashed. Among them was Nikole Flax, who was chief of staff to Lerner’s boss, then-deputy commissioner Steven Miller.

Miller later became acting IRS commissioner, but was forced to resign last year after the agency acknowledged that agents had improperly scrutinized tea party and other conservative groups when they applied for tax-exempt status. Documents have shown some liberal groups were also flagged.

Investigators from the House Ways and Means Committee interviewed IRS technicians Monday. The technicians said they first realized that Lerner’s emails were lost in February or March – months before they informed congressional investigators, said a statement by two top Republicans on the Ways and Means Committee, chairman Dave Camp of Michigan and subcommittee chairman Charles Boustany of Louisiana.

The two lawmakers called on the Justice Department to appoint a special prosecutor to investigate the IRS, something Attorney General Eric Holder has declined to do in the past.

Lerner’s computer crashed in the summer of 2011, depriving investigators of many of her prior emails. Flax’s computer crashed in December 2011, Camp and Boustany said.

In emails provided by the IRS, technicians said they sent the computer to a forensic lab run by the agency’s criminal investigations unit. But to no avail. The IRS was able to generate 24,000 Lerner emails from the 2009 to 2011 period because Lerner had copied in other IRS employees. Overall, the IRS said it is producing a total of 67,000 emails to and from Lerner, covering the period from 2009 to 2013.