PITTSBURGH --
8:25 PM UPDATE: Police say the threat was phoned in from a pay phone on Carson Street by an unknown man.

6:55 PM UPDATE: State police will hold a press conference at 8 p.m. tonight.

6:50 PM UPDATE: The Liberty and Fort Pitt tunnels have reopened after a security sweep.

6:45 PM UPDATE: The FBI has been called in to help state police with the investigation.

6:20 PM UPDATE: Channel 11 has just learned the Squirrel Hill Tunnel has reopened to traffic after a security sweep.

6:15 PM UPDATE: Channel 11 has just learned the Liberty Tunnels have just closed.

6:10 PM UPDATE: Officials say the threat was called into 911 around 4:45 p.m. Thursday.

5:45 PM UPDATE: PennDOT said the tunnels will be closed for about a half hour.

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Police said on Thursday they received a threat of a bomb inside the Squirrel Hill and Fort Pitt Tunnels.

Both tunnels are shut down in both directions.

Police said they closed the tunnels in order to do a sweep.

PennDOT said the tunnels will be closed for about a half hour.

Officials are turning traffic around.

Traffic is backed up in all directions.

Watch Channel 11 News for continuous updates on this developing story.