Police charged four men with producing chemical weapons and other terrorism offenses Saturday in the discovery of the deadly poison ricin in a London apartment.

The men, described only as North Africans, were among seven suspects arrested earlier this week after an anti-terrorist raid uncovered traces of the poison, which can kill within days. There is no antidote or treatment.

The four — Mouloud Feddag, Sidali Feddag, Samir Feddag and Mustapha Taleb — were charged with "possession of articles of value to a terrorist" and with "being concerned in the development or production of chemical weapons."

A fifth suspect, Nasreddine Fekhadji, was charged with forgery and counterfeiting offenses.

The men are to appear in court Monday.

A sixth man arrested for alleged possession of drugs and immigration offenses was expected to be released on bail, police said. A seventh man was released to the custody of immigration officials.

Ricin (pronounced RICE-in) is derived from the castor bean plant, which is grown around the world. The poison is relatively easy to produce and has been linked to the Al Qaeda terror network and Saddam Hussein's regime in Iraq.