On the heels of a horrific limousine crash that killed 20 people in upstate New York, the Senate’s top Democrat is pointing to glaring gaps in safety data that he says exist because federal officials have not done enough to investigate limo wrecks.

Sen. Chuck Schumer is pointing a spotlight at the National Transportation Safety Board, which he says hasn’t thoroughly investigated a single limousine crash in the last three years.

His criticism comes a week after a stretch limo loaded with 18 people ran a stop sign and crashed at the bottom of a long hill in Schoharie. Everyone in the limousine died, including four sisters, along with two pedestrians.

“The sad fact here is that right now everyone is talking about limo safety when we could have been studying it for the past few years,” Schumer said. “The NTSB knows they need to fix this situation so we can have as much information as possible available.”

The agency — charged by Congress to conduct independent probes and make safety recommendations — agreed to investigate limo crashes on a case-by-case basis after a 2015 wreck that killed four women on New York’s Long Island.

But Schumer says that since then, multiple crashes should have been investigated and would have netted “critical safety data” about the structure and safety components of limousines. Federal crash data compiled by The Associated Press shows there were seven limousine crashes in 2015 and two in 2016.

Factory-built limousines must meet stringent safety regulations. But luxury cars converted to limos, like the one in last week’s crash, often lack such safety components as side-impact air bags, reinforced rollover protection bars and accessible emergency exits.

Few federal regulations govern limos modified after leaving the factory, and regulations often vary by state.

Eric Weiss, a spokesman for the NTSB, declined to comment on Saturday.

In a 2015 letter, then-NTSB Chairman Christopher Hart said the board shared Schumer’s concern that “relatively little information is available about how stretch limousines perform in a variety of crash scenarios.”

Schumer says the NTSB should recommit and follow-through on the agency’s promise to investigate limousine crashes across the U.S. — not just those that result in multiple deaths — in order to gather crucial safety information and determine whether regulations or laws need to be changed.

The board must also issue immediate safety recommendations on stretch limousines as it investigates last weekend’s crash, he said.

While authorities continue to investigate the cause that wreck, New York prosecutors have charged the operator of the limousine company, Nauman Hussain, with criminally negligent homicide, saying he allowed an improperly licensed driver to operate an “unserviceable” vehicle. Hussain has pleaded not guilty and has declined to comment on the crash.

(AP)