Two U.S. senators are looking into a potential deadly danger for passengers riding in the back seats of cars.

Sen. Ed Markey, D-Mass., and Sen. Richard Blumenthal, D-Conn., sent a letter to 17 automakers requesting detailed information on the strength of front seats and the number of known seat collapses.

Auto safety advocates have long warned that front seat backs could collapse in rear impact crashes, injuring passengers riding in the back.

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"We asked the government in 1974, 'Let’s upgrade the standard,'" said Clarence Ditlow of  the Center for Auto Safety. "The government says' OK, you're right we'll upgrade it.' But 30 years went by and nothing happened."

The National Highway Traffic Safety Administration said they have not created new rules for seats because of the absence of data demonstrating real world benefits.

"When the government says we don’t have any information showing a problem, it is because they aren’t looking for a problem," Ditlow said.

The Center for Auto Safety estimates there could be 100 deaths a year because of front seats that collapse. The senators are giving automakers a one-month deadline to provide the details they've requested about seat backs.