Tempe City Hall workers were detained in the City Council chambers this morning during a sweep by FBI agents, city officials confirmed.

City manager Charlie Meyer confirmed that the sweep was conducted but declined to comment further.

The FBI declined to comment except to say that the City Hall was not the target of the investigation. Tempe Police spokesman Steve Carbajal said the sweep was carried out in conjunction with Tempe police, but he declined further comment.

The Arizona Republic was tipped off by an anonymous caller this afternoon. The caller said federal agents kept a number of employees in the City Council chambers for about two-and-a-half hours. The curtains were drawn and employees were told to turn off their cellphones, the caller said.

Check back later for updates.