Police in the US are looking for troubled singer Sinead O’Connor following reports she is threatening to jump off a bridge.

A spokesman for the Chicago Police Department said the force was alerted at 3.30pm local time and the whereabouts of the 49-year-old Irish singer were unknown.

Officers received a report from police in Ireland that O’Connor had said she planned to jump off a bridge in the US city, the spokesman said.

Sinead O'Connor
Sinead O’Connor (Balazs Mohai/AP)

The case is not being treated as an “active missing persons investigation” at this time but officers have been told to be on the lookout for O’Connor, he added.

The Nothing Compares 2 U singer, who has a history of mental health problems, sparked a police search in May after she went missing. She failed to return from a bike ride in the Chicago suburb of Wilmette but was later found safe.

Sinead O'Connor
Sinead O’Connor (Jean-christophe Bott/AP)

In December, O’Connor wrote on Facebook that she has been detained in hospital for a mental health evaluation.

A month earlier she wrote another Facebook post claiming she had overdosed on pills in a hotel room in Ireland. She was later found safe and taken to hospital.