LONDON (Reuters) - Parcel bombs sent to London’s main airport and two other major transport hubs on Tuesday had Irish stamps and Irish police are now assisting British counter-terrorism officers, broadcaster Sky News said on Tuesday.

No one was injured by the bombs, one of which caused a small fire in an office building at London’s Heathrow airport and the others were discovered at London City airport and the city’s biggest rail station, Waterloo.

“At least two of the packages had Irish stamps,” Sky News said. “Irish police are assisting with the investigation.”

London’s police force declined to comment on the report.