Seabird oil deaths: Minister investigates tanker discharges 19 April 2013 Last updated at 08:58 A government minister has said the UK is investigating discharges by chemical tankers after hundreds of birds washed up dead along the south coast. Seabirds have been washed up covered in oil additive polyisobutene (PIB) in two separate incidents this year. Dorset South MP Richard Drax wrote to transport minister Stephen Hammond calling for tighter controls. Mr Hammond said results of the inquiry will be passed to the International Maritime Organisation (IMO). Member states need to submit findings to the IMO showing evidence that the substance should be reclassified. Madness The RSPB said more than 700 birds were affected in Devon and Cornwall since 10 April, while hundreds were found covered in the substance, mainly in Dorset, in February. In the letter, Mr Hammond said a number of other European countries were also looking into discharges from ships. Currently, PIB - used by ships to make their engines work more efficiently - can be released legally under certain conditions. The RSPB has called for discharges to be outlawed while Mr Drax said the situation was "madness." Mr Hammond wrote: "As to whether the current arrangements for the carriage of PIBs are adequate, a number of European countries, including the UK, are currently investigating the discharge of high viscosity products by chemical tankers and the resulting residues washing up on beaches. The result of this will be submitted to the IMO for consideration of whether any changes need to be made to the existing requirements. The Maritime and Coastguard Agency said it was trying to determine the source of the latest incident but ended inquiries into the first discharge admitting it was "highly unlikely" the ship could be found.