PARIS (AFP) - Workers found six petrol containers attached to a "crude detonator device" under several trucks at a cement works in Paris on Thursday (Oct 5), sources close to the inquiry told AFP.

The trucks, found in the French capital's north-eastern 19th arrondissement, belonged to Franco-Swiss cement company LafargeHolcim.

"Workers discovered the containers as they went to work this morning," one source told AFP.

Bomb disposal experts rushed to the site and police cordoned off the area, situated in a working-class district.

The incident comes as anti-terrorism police investigate the discovery of several gas canisters and a cell phone detonator in western Paris on Saturday, but a source said there was no apparent link between the two.

Six people are in custody over the canisters placed in the hallway of a building in the wealthy 16th district, including two who were on watchlists for Islamic extremism.

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

Several women, who had received instructions from the Islamic State in Iraq and Syria (ISIS) group to carry out an attack, were arrested.

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

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

Earlier this year, 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.