French newspaper Le Monde has reported that the Kouachi brothers, accused of the Hebdo killings, were killed in a raid that began around 4pm UK time this afternoon.
Some media organisations are also reporting that the hostage is a worker at the printing business.
The hostage situation at a supermarket in Paris appears to have been resolved simultaneously.
Major news organisations reported that French security personnel were seen advancing towards the building beforehand in the town of Dammartin-en-Goële, north-east of Paris prior to the raid.
At 4pm the BBC’s Chris Morris reported: “There was a sudden burst of intense gunfire lasting about a minute, several explosions as well as possibly grenades, more gunfire and now it has gone quiet again. We are a few hundred metres from the building.”
The suspects hijacked a car and ended up at the small industrial estate in the town.
CTD specialises in signage, vehicle graphics, promotional items and a range of wide-format print applications. It runs offset and digital print kit.
The number of employees at the business is not known, although reports have described it as a small business.
Meanwhile, Charlie Hebdo has upped the print run for its next issue to one million. The usual print run for the satirical weekly is 60,000.
The remaining staff at Charlie Hebdo have put a defiant message on the magazine's website. It said: “Because the pen is always above barbarism… because freedom is a universal right… because you support us…”
It will publish an issue Le Journal des Survivants created by the survivors of the attack next Wednesday (14 January).