Train services around Reading in Berkshire were disrupted by a fire involving a gas cylinder, which it was feared might explode.
Crews were called to Kennet Weir business park in Theale at 0930 GMT.
A 200m (650ft) cordon was set up and workers were evacuated from offices. A smaller cordon remains in place while the cylinder is monitored.
The earlier exclusion zone included the railway, meaning trains from Reading to Westbury were halted until 1530 GMT.
Train services to the west of England were diverted around the area and did not call at any stations between Reading and Westbury during the incident.
Bus replacements operated between Reading and Bedwyn and Pewsey and Swindon.
A specialist robot brought in from the London Fire Brigade was used remotely to assess the cylinder. About 30 firefighters attended the scene.
BBC News Berkshire, 28 February 2011 19:38
TRAINS are running normally through Newbury and Reading following disruption earlier today (Monday) due to a major fire at an industrial park in Theale.
A thermal imaging robot was used by the London Fire Service to help with a blaze at Unit two at Kennet Weir in Arrowhead Road, that caused more than 100 people to be evacuated from nearby offices.
The blaze, which broke out at Alan Hadley Recycling and Waste Management in Kennet Weir Business Park at about 9.15am, caused an Acetylene gas cylinder to overheat.
A 200-metre cordon was enforced in case the cylinder, which is used for welding, exploded.
This resulted in the closure of Arrowhead Road, Brunel Road, and Waterside Road.
Speaking at the scene at about 1pm today, Lincoln Ball, station manager at the fire headquarters in Dee Road, Tilehurst, said: “We immediately put in place a 200m cordon from the business premises.
“We believe that this has affected about six businesses with about 100 to 150 people evacuated.
“Acetylene is a gas unlike any other which means the cylinder can self heat and inevitably goes bang. This can create a 25 meter fire ball."
“If we get indications that the cylinder is not self heating we can reduce the cordon but we will be here for 24 hours because it’s a 24-hour operation."
“The robot is testing for heat and whether the cylinder is steaming off, it updates every fifteen minutes."
“The robot is specifically used for Acetylene gad cylinders and for explosives.”
He said that the cause of the fire was still being investigated.
The cordon was reduced to 50 metres at about 1.30pm and Network Rail has said trains are now running normally through Theale.
Ambulance crews were at the scene but there were no reported injuries.
Mark Taylor/James Williams, Newbury Today