* Chelsea beat Southampton 4-2 to extend Premier League lead
* Eden Hazard scored first for Chelsea inside five minutes
* Former Chelsea midfielder Oriol Romeu equalised
* Chelsea captain Gary Cahill’s header put Chelsea ahead just before halftime
* Striker Diego Costa scored two second-half goals
* Ryan Bertrand added injury-time consolation for Saints
* Chelsea at Everton next, Southampton host Hull City
LONDON, April 25 (Reuters) - Buoyant Chelsea extended their Premier League lead to seven points on Tuesday, as goals from Eden Hazard, captain Gary Cahill and two from a buzzing Diego Costa earned them a 4-2 win over Southampton.
It took them less than five minutes to open a lead when Costa controlled a pass from Cesc Fabregas, surged forward and cut the ball back for the advancing Hazard, who angled his shot into the bottom corner of Fraser Forster’s net.
Former Chelsea midfielder Oriel Romeu equalised in the 24th minute, forcing home from close range. But Chelsea, boosted by their FA Cup semi-final win over nearest rivals Tottenham Hotspur at the weekend, took the lead again just before halftime when Cahill headed in from a N‘Golo Kante punt into the area.
Costa, who has been misfiring of late, took his chance in the 53rd minute and fired in a header -- his 50th Premier League goal -- then added a second for good measure in the 89th after a one-two with Hazard.
Southampton scored an injury-time consolation goal through another former Chelsea player Ryan Bertrand. (Reporting by Clare Lovell; Editing by Toby Davis)