Investment firm 3i infrastructure announced on Tuesday it would pay £109m for a 50% stake in Danish company ESVAGT.AMP Capital has agreed to buy the other half of the emergency rescue company from Maersk Group.The deal was pending clearance from the European Commission under merger regulations.3i chairman Peter Sedgwick said ESVAGT has a strong track record of providing critical safety services to the offshore oil and gas industry."This investment fits well with our strategy of investing in mid-market economic infrastructure businesses which have a strategic position and are asset-backed, and which can deliver long-term stable yield to our shareholders, underpinned by revenues contracted over the medium term."Shares in 3i were up 0.17% to 166.49p at 0806 BST.