MONTREAL - Charges are expected to be laid today against four youths detained after Thursday's smoke-bomb attacks on the Montreal subway system.

The suspects, one man and three women, turned themselves in to authorities Friday.

They are scheduled to appear in court via video conference today to face charges of hoax regarding terrorist activity, conspiracy and mischief over $5,000

The man, 22, will also face a charge of possession of a prohibited weapon.

Smoke-bomb attacks on several metro stops caused a shutdown at the height of rush hour Thursday morning, creating a frustrating and traffic-clogged commute for many thousands of Montrealers.

A merchants' association and a conservative economic think-tank have estimated that the incident cost Montreal several million dollars in lost productivity.

It is estimated that the subway closure cost the city several million dollars in lost productivity.

Student leaders have distanced themselves from the attacks, saying they won't help put an end to the conflict.

Earlier Friday, police spent hours searching the Hochelaga-Maisonneuve apartment of two of the suspects.

Some students at UQAM told CTV Montreal on Friday that acts of violence and vandalism aren't helping their cause.

"When things like this happen it hurts the movement," one student said.

Lafreniere said they are still seeking information from the public regarding what happened at the Jean-Talon and Prefontaine stations.

The four suspects were expected to be arraigned Saturday.