Paris (AFP) - Workers found several petrol containers and burnt matches under trucks at a cement works in Paris Thursday, triggering a security scare, but the incident was not thought to be terrorism-related.

The crude devices found under parked trucks at a facility belonging to Franco-Swiss cement maker LafargeHolcim were never at risk of detonating, investigators said.

Video surveillance footage from Wednesday night showed two people trying to set fire to the containers, a police source told AFP.

When drivers arrived for work in the morning they noticed bottles of fuel under the vehicles, with burnt matches attached.

Bomb disposal experts rushed to the site and police briefly cordoned off the area but by the afternoon activity had returned to normal.

The incident comes as anti-terrorism police investigate the discovery of several gas canisters and a cell phone detonator in the hallway of a building in western Paris on Saturday.

Six people are in custody over the incident, including two who were on watchlists of known Islamist radicals.

In September last year, five full gas canisters were found in a car abandoned near the Notre Dame cathedral in central Paris.

Several women, who had received instructions from the Islamic State (IS) group to carry out an attack, were arrested over that incident.

France has suffered a series of jihadist attacks since 2015 which have left 241 people dead.

Cement giant Lafarge is under investigation over claims that it indirectly funded IS and other armed groups in Syria in order to keep a plant running in a war zone.

The company admitted it had resorted to "unacceptable practices" to continue operations at a now-closed cement factory in northern Syria in 2013-14, after most French groups had quit the war-torn country.