By NBC News staff and wire services
Updated at 11:00 a.m. ET: Authorities are investigating a bomb threat made at a Boeing plant in Delaware County, Pa., on Tuesday morning.
A Boeing spokesperson told NBCPhiladelphia.com that several hundred employees have evacuated the south campus of the Boeing Plant in Ridley Park, Penn., where the H-47 Chinook helicopter is manufactured.
The evacuations happened between 7:30 and 8:30 a.m. ET, after officials became aware of the threat, The Delaware County Daily Times reported, and bomb-sniffing dogs are going through the facility.
According to Ridley Township police, a note was left in a bathroom claiming four explosives were planted inside of one of the hangers, the Daily Times reported.
This story is still developing. Please check back for updates.
NBCPhiladelphia.com's Kelly Bayliss contributed to this story.
More content from NBCNews.com:
- No negative impacts from repeal of 'don't ask, don't tell', study finds
- His American Dream is dead, killed by the recession
- Catholic college course scrutinized for calling homosexuality deviant
- Quiet time: NYC's 9/11 memorial at dusk
- SEAL explains why bin Laden was dangerous when killed
- Video: Police release video from Sikh shooting
- 'Jew Pond' name officially changed on US maps