Second bomb threat of the day on Metro

Updated at 5:37 p.m.

Metro service was disrupted by a bomb threat for the second time Tuesday.

This time, a caller told Metro Transit Police that there was a note mentioning a bomb on a train in Arlington, Metro spokeswoman Sherri Ly said. Police stopped the train at Pentagon City and searched it with bomb-sniffing dogs. The dogs found neither a bomb nor the note, Ly said.

While the dogs were searching, Blue and Yellow Line trains were single-tracking from Pentagon City to National Airport, causing delays on both lines.

Earlier in the day, Blue, Orange and Silver Line trains were delayed when authorities stopped a Silver Line train to search it for a bomb. That train had a message scrawled on a spot where an advertisement would normally go: “There is a bomb on this train.”

Someone wrote "There's a bomb on this train" on @MyAdventureHat #wmata car this AM

cc @unsuckdcmetro @dcmetrosucks pic.twitter.com/nlzYxjUDyq

— Cloture Club (@ClotureClub) September 1, 2015

Metro spokesman Mike Tolbert said that the train car where the threat was reported at Pentagon City was not the same one with the menacing graffiti. He said investigators do not know if the two threats are related.