BP successfully lobbied against tighter environmental controls by regulators in Texas, saving $150m in monitoring and equipment upgrades prior to the fatal refinery explosion in 2005, internal documents show.

The proposed controls would have forced BP to invest in upgrading the exhaust system on the unit that exploded to include a flare. The US Chemical Safety Board (CSB) said the upgrade would have prevented – or at least mitigated – the blast that killed 15 and injured 500.