A BUSY entrance to Southampton docks was closed and an exclusion zone put in place as a freight container threatened to explode yesterday.

Pressure inside the 40ft container grew so much its rectangular shape became almost cylindrical.

Police shut the bridge entrance to Dock Gate 20 while the container, full of 30 tons of scrap metal, was moved to a safe area of the Freightliner depot.

Paramedics were on stand-by while firefighters used thermal imaging cameras and hand-held gas monitors to try to establish what made the container, pictured right, bulge.

Gases A build-up of gases caused by putting different types of metal in the same sealed container has been blamed and its doors were opened to ventilate it.

Keith Gray, business planning director for Freightliner, told the Daily Echo the container had travelled by rail from Leeds and was due to be shipped to Hong Kong.

He said: "So much scrap metal is exported out of the UK and this is certainly not a regular occurrence.

"The container was not considered hazardous when it was loaded or it would have had a label on it saying what to do in an emergency.

"It cannot carry on its journey in the condition it's in and it is now down to the customer in Hong Kong to tell us what he wants done with the contents."

He said two further containers of scrap metal have been put on hold to be checked they are safe.

A 100-metre exclusion zone was placed around the container from 10.15am until it was opened at 1.30pm.

Traffic was briefly diverted to Dock Gate 10 while the container was moved along the railway under the bridge.