California lawmakers asked the state’s top air pollution officials Tuesday why it took them years to figure out that Volkswagen was cheating on emissions tests and putting pollution-spewing diesel cars on the road.

Annette Hebert, chief of the Emissions Compliance division at the California Air Resources Board, told legislators during a hearing that the measurement devices used to test the vehicles are fairly new.

But since that technology has been available for about four years, her answer did not satisfy some lawmakers.

“You would have detected it and we could have taken these vehicles off the road, four years or five years or maybe six, by the time we get around to it, off the road earlier,” Sen. Richard Roth, D-Riverside, said.

Roth said the state’s scientists should have gotten better at spotting vehicles that cheat on emissions test because of a previous scandal involving diesel vehicles in 1998. Back then, the polluters in question were trucks.

In another development Tuesday, state officials said they doubt that Volkswagen will ever be able to put a full-proof fix in place. So, for now, nearly 80,000 such vehicles in California and more than 600,000 around the country remain on the road.

They can emit more than 40 times the amount of pollution that meets federal standards. Volkswagen has submitted proposals for fixes, which officials at the Air Resources Board deem insufficient.

CARB scientists exposed Volkswagen’s cheating last fall, after the company finally admitted to it during a September meeting, the agency said. That admission came after CARB representatives repeatedly confronted Volkswagen with a set of test results that didn’t match: the cars would perform fine in laboratory testing, but fail pollution tests on the road.

The company ultimately admitted that it had installed a defeat device, software that detects when a car is being tested in a lab and alters the level of emissions that would be emitted on the road, according to a CARB spokesman. But, CARB did not begin that process until after European regulators told the California agency that it was having trouble matching results on the road to results in a lab.

Volkswagen representatives did not attend Tuesday’s hearing and did not respond to a request for comment. The company is now the target of multiple lawsuits from drivers, but one state lawmaker asked Tuesday if anything more can be done.

“Do you know what authority we have, what legal options we have to actually put people in prison for a crime they’ve already admitted they’ve done,” Sen. Mark Leno, D-San Francisco, asked the CARB officials.

They said their agency cannot hold Volkswagen criminally liable, but others might. The U.S. and California Departments of Justice are both investigating.

State officials plan to do more road testing of vehicles in the future.