Russia has grounded all flights of its Proton-M rockets for another three and a half months, following a crash last December that destroyed one of the rockets minutes after liftoff.

The uncrewed Progress MS-04 cargo ship carrying supplies for the International Space Station (ISS) broke up in the atmosphere over Siberia about six minutes after it left the launchpad, in an incident that investigators blame on faulty engine parts. A report indicates that some important components in the second and third stages of the Proton-M rocket may have been switched out by workers during the construction process. Safety inspections of the other Proton-M rockets are currently underway. Until they are finished, the Proton-M, a staple of the Russian rocket fleet, will remain grounded.

A report published in the Kommersant newspaper reported that the defect that caused the ship to break apart in December could be traced to the Voronezh plant, which builds the Proton-M and Soyuz rocket engines. The chief of the Voronezh plant quit earlier this month.

"Instead of using materials containing precious metals .... less heat-resistant components were used, which are normally used for other engine models," says a report published in the Kommersant newspaper, according to Deutsche Welle.

The replacement parts would have been cheaper in the short term, but cutting corners ultimately proved disastrous for the Progress MS-04.

"According to preliminary information, the contingency took place at an altitude of about 190 km over remote and unpopulated mountainous area of the Republic of Tyva," a statement from Roscosmos, Russia's space agency, said at the time of the crash. "The most of cargo spacecraft fragments burned in the dense atmosphere. The State Commission is conducting analysis of the current contingency. The loss of the cargo ship will not affect the normal operations of the ISS and the life of the station crew."

The crash destroyed 2.6 tons of food, fuel, and other supplies bound for the ISS.

At the Voronezh plant, workers had evidently been directed to "switch technology and documentation," according Russian Deputy Prime Minister Dmitry Rogozin.

"All those responsible for switching document and technology would be harshly punished," Mr. Rogozin said. "Three Proton-M rockets will be dissembled and their second and third-degree engines replaced."

The tampering may raise concerns beyond the confines Russia's space program as well. Currently, Russia is the only country capable of launching astronauts to the ISS, which they achieve using Soyuz rockets that are also manufactured at the Voronezh plant. There is currently no evidence to indicate that their engines were also tampered with in a similar manner to the Proton-M.

This is far from the first time concerns have been raised over Russia's space program and rocket quality control. The Proton-M seems to be particularly prone to mishaps in recent years, with technical mishaps leading to crashes in 2013, 2014, and 2015. All of these failures involved unmanned rockets.

Despite the recent failures, however, Russia's space agency has promised to inspect all of its Proton-M rockets to make sure they are really ready for launch in three and a half months.

Get the Monitor Stories you care about delivered to your inbox. By signing up, you agree to our Privacy Policy

"A necessary check of engines with possible technical defects will be made," Roscosmos said in a statement.

This article contains material from the Associated Press.