Canada’s Garda World Security has confirmed that it is considering making a cash offer for some or all of the UK outsourcing company G4S.

G4S shares jumped 30% on the news, heading for their biggest single-day gain and lifting the company’s market value to about £3.8bn.

The world’s largest security company, G4S has UK government contracts to run facilities including prisons and immigration centres, as well as providing security staff for a wide range of organisations and live events. It also operates a range of outsourced services for the NHS.

The statement from privately held Garda World came after the London Evening Standard reported market talk of a potential bid. G4S declined to comment on the report.

“Garda World notes the recent market speculation in relation to G4S and confirms that it is in the preliminary stages of considering an approach to the board of G4S regarding a possible cash offer for the company, or a part thereof,” the Canadian company said.

G4S, which has more than 500,000 employees across 90 countries, has been working to rebuild its reputation after a series of scandals, notably a failure in 2012 to provide enough guards for the Olympic Games in London.

G4S said in March it had received interest from potential bidders for its cash business, which includes Cash 360 machines operated by retailers and a cash transportation business.

According to Garda World’s website, the company also owns a “cash solutions” business, apart from security services.