Concrete attacks: A12 in Essex closed for search Published duration 4 December 2011

image caption A concrete bollard that hit the Nissan had been stolen from a house in Galleywood

An Essex road where concrete blocks were dropped onto cars from a bridge was closed on Sunday night amid fears of a repeat of the incident.

Police closed sections of the A12 just after 19:30 GMT after a woman reported seeing a man with a concrete block on the Wantz Road Bridge, at Margaretting.

A woman was seriously hurt on Thursday when a bucket-sized block hit the Nissan she was travelling in.

A large stone had hit a Vauxhall Astra earlier that night.

The 57-year-old woman who was hurt remains in a serious but stable condition. The two incidents are being treated as attempted murder.

Police closed parts of the road on Sunday while they searched the area.

Essex Police said an immediate search of the carriageway, bridge and surrounding roads was undertaken, but officers could find no trace of unusual activity.

Report 'not malicious'

Various sections of the road on both carriageways were then periodically closed while all bridges and surrounding areas were searched, taking several hours and causing disruption to traffic travelling along the A12 between Boreham and Brentwood.

image caption A large stone was dropped from a bridge over the A12 on to a Vauxhall Astra on Thursday

A police spokesman said: "This was not a malicious report. It was genuine and we would encourage such calls to our control room.

"We are sorry for the disruption we caused to the many motorists, but they and the surrounding communities understand that road safety is of paramount importance, as is catching the perpetrators behind these attacks."

Meanwhile, new lines of inquiry have emerged in the investigation into Thursday's incidents and police said they had had a "fantastic" response from the public.

Officers have said the "despicable" attacks had potentially fatal consequences.

Forensic examinations

A mother and daughter from Brentwood were left shaken when a large stone dropped from Fryerning Lane bridge, near Ingatestone, at 21:20 GMT on Thursday.

It smashed through the windscreen of their Astra but did not injure them.

Officers have released an image of the stone, which measures about 30cm by 30cm. They believe it was stolen from a garden.

Eight miles along the A12, a concrete bollard the size of a bucket smashed through the windscreen of the Nissan from West Hanningfield bridge, near Galleywood, at about 22:00 GMT.

The front-seat passenger suffered severe face and chest injuries and had to be cut from the car, while her husband, aged 56, suffered minor cuts and bruises.

Police have revealed that one of the blocks had been stolen from a house near Galleywood.

'Perpetrators not identified'

Detectives are looking back at more than 30 similar incidents over the past three years for any links to Thursday's attacks and are carrying out forensic examinations of items recovered from the bridges.

They are keen to receive details of suspicious activity, reports of other incidents or information about the removal of hardcore or building rubble.

Det Ch Insp Keith Davies said: "The public response has so far been fantastic in terms of from our house-to-house inquiries as well as people calling us with information.

"However, we still have not yet identified the perpetrators behind these attacks so continue to encourage people to come forward.

"The investigation is taking shape and we're now piecing together the detail that is being gathered."