Elon Musk, chief executive of SpaceX, speaks during the 67th International Astronautical Congress in Guadalajara, Mexico, on Tuesda (Susana Gonzalez/Bloomberg)

A group of 10 Republican members of Congress wrote Thursday that they are increasingly concerned about SpaceX’s ability to safely fly NASA astronauts and national security satellites after the company recently suffered its second rocket explosion in just over a year.

In a letter to the Air Force, NASA and the Federal Aviation Administration, the group said SpaceX should not be leading the investigation into its most recent failure, and that authority should be turned over to the federal government “to ensure that proper investigative engineering rigor is applied.”

Last year, an unmanned Falcon 9 rocket exploded a couple minutes after it launched a resupply mission to the International Space Station, destroying $118 million worth of cargo. Then, earlier this month, another Falcon 9 rocket blew up as it was being fueled ahead of an engine test. A $195 million commercial satellite sitting on top of the rocket was lost in the fireball.

“These failures could have spelled disaster, even loss of life, had critical national security payloads or NASA crew been aboard those rockets,” wrote the members, many of whom represent states where SpaceX’s chief competitor, the United Launch Alliance, has a strong presence.

SpaceX declined to comment. After the Sept. 1 explosion, SpaceX founder Elon Musk said on Twitter that the Dragon capsule would have been able to abort in time, ferrying the astronauts on board to safety.

The company has said it is narrowing down the cause of the explosion, pinpointing a breach in a second-stage helium system. Earlier this week, Musk said the investigation was “vexing and difficult.” He stressed that finding out what went wrong is the company’s “absolute top priority” but said what actually caused the explosion was still unknown.

“We’ve eliminated all of the obvious possibilities for what occurred there,” he said. “So what remains are the less probable answers.” He didn’t say what those might be.

In the wake of the explosion, NASA has said it stands by SpaceX and the Air Force has said it shouldn’t affect the company’s certification.

SpaceX, which relies heavily on the federal government for revenue, holds lucrative contracts with NASA to fly cargo and eventually astronauts to the space station. It also holds a certification from the Air Force that allows it to compete for contracts to launch national security satellites against the United Launch Alliance, the Colorado-based joint venture of Lockheed Martin and Boeing.

The members of Congress, led by U.S. Rep. Mike Coffman (R-Colo.) questioned whether the Air Force should reconsider SpaceX’s certification. And they asked NASA whether it still plans to allow SpaceX to use the Falcon 9 for its cargo and crew missions.

Since there was no loss of life or injury and no outside property was extensively damaged, federal regulations call for the launch providers to conduct the investigations with oversight from the FAA. NASA and the Air Force are also helping with the investigation.

NASA declined to comment on the matter. The Air Force said it would respond to the members of Congress directly. The FAA did not immediately respond to requests for comment.