Update: Metro Says 'Heat Kink' Caused Derailment Friday

Update, 10:30 p.m.: WMATA said Green Line service between Prince George's Plaza and Fort Totten will remain suspended Sunday as they make repairs to about a 1,000-foot area of the tracks.

According to Metro's website, the three train cars that left the track Friday were re-railed.

Free shuttle buses will operate between the closed stations and WMATA says normal service should resume by Monday.

Original Post, 12:37 p.m.: WMATA investigators have determined the cause of the derailment Friday along the Green Line in Prince George's County.

According to a release on Metro's wesbite, a misalignment of the rails or "heat kink" was what made three rail cars come off the tracks in an inbound tunnel approaching West Hyattsville.

"Heat kinks are short sections of misaligned track caused by the expansion of metal rails in extremely high temperatures and prolonged exposure to direct sunlight. When the expanding rail cannot be constrained by cross-ties and ballast, the rail may expand outward from the normal track alignment," WMATA officials wrote on their website.

Although no one was injured, it caused major delays along the Green Line, as the tracks were closed between the Fort Totten and Prince George's Plaza stations.

WMATA will continue to investigate the incident to determine contributing factors.

The Green Line service remains suspended between Fort Totten and Prince George's Plaza stations Saturday, while Metro crews work to put the train cars back on the track and repaid the track. All other track work was cancelled.

Free shuttle buses will operate between the closed stations and WMATA says normal service should resume by Monday.