A cargo ship packed with potentially explosive ammonium nitrate remains adrift in the English Channel off the coast of France.

The Maltese-registered Ruby is carrying 20,000 tonnes of the chemical compound that it picked up from Russia in August.

When improperly stored and exposed to stress (such as heat and pressure), it can become increasingly unstable and explode.

The 183-metre-long ship is carrying enough ammonium nitrate to potentially cause an explosion equivalent to the power of an “atomic bomb”.

French authorities said they are keeping a close eye on the Ruby’s movements, as it tries to head for Malta, where it is expected to arrive on October 11, according to the website Marine Traffic.

“We are in regular contact with the shipowner who is cooperating,” Etienne Baggio, spokesperson for the maritime prefecture of the English Channel.

“In fact, they have dispatched a tugboat to provide assistance in the anchorage area where it currently is.”

The dangers posed by the improper storage of ammonium nitrate were vividly exposed in Beirut four years ago.

2,750 tons of ammonium nitrate had been stored in a warehouse, after being confiscated from a Russian-owned ship the MV Rhosus in 2013.

Seven years later a massive explosion ripped through Beirut’s port, killing 235 people and injuring over 6,000.

Ammonium nitrate is normally a key component in producing agricultural fertiliser, but is also used in explosives for mining.

The Ruby got into trouble after being caught in a violent storm at sea, as it was making its way to Malta

It sought shelter at the Norwegian port of Tromsø. However, the severe weather had heavily damaged the Ruby’s propeller, rudder and hull, forcing officials to turn the vessel away due to fears over its safety.

The Ruby then headed to Lithuania, but was refused entry to the port in Vilnius, before ending up in the English Channel.

Officials in Malta have told the ship’s owners they will have to get rid of the ammonium nitrate, before docking there.

“The ship will only be authorised to dock in Malta if it empties its cargo, otherwise it will not be authorised to enter our territorial waters,” authorities said.