A strange vandalism spree appears to be hitting office towers in downtown Halifax — someone is throwing objects down elevator shafts.

Four elevator shafts were suddenly shut down last week at 1801 Hollis St. after tenants on multiple floors reported a loud banging coming from inside.

The sound was a metal panel bouncing off the elevator shaft walls as it plummeted to the basement.

The 1801 Hollis St. building is the third-tallest tower in Halifax and has 22 storeys. (Brett Ruskin/CBC)

"The source of the problem was not mechanical and at no time were passengers in danger," said an email to the tower's tenants from CREIT Management, the building's manager.

This isn't a first for Halifax.

Going up? Elevator incidents on the rise

Similar incidents have happened in at least three other buildings in the city.

Earlier this month, tenants of a Mumford Road office building — including CBC News in Halifax — were sent an email from the property manager about falling signs.

"Debris, including Wet Floor signs, have been dropped by persons unknown into the elevator shafts," said the email.

"This has happened on more than one occasion and in one instance, narrowly missed a technician working in the shaft."

According to a notice from CREIT Management, the same thing has happened at Purdy's Wharf and Scotia Square.

It's not clear whether the incidents are related.

This bank of elevators at 1801 Hollis was shut down this week, after tenants reported a loud banging inside. (Brett Ruskin/CBC)

Police investigating

Halifax Regional Police are now looking into the incident at 1801 Hollis St.

Const. Dianne Woodworth confirms police received a report on Sept. 14 of a suspicious person at the building, involving an object thrown down one of the elevator shafts.

She said police had not received any other reports of similar incidents.

Each of the emails obtained by CBC News sent to various towers' tenants advised anyone who sees suspicious activity near elevators to call the building manager, or police.