Cheikhou Kouyate struck in the third minute of injury time to deny Norwich City victory at Upton Park as Slaven Bilic's side missed out on the chance to move above Manchester City with a 2-2 draw at Upton Park.
Both sides secured positive results last weekend and both had chances to open the scoring within the first two minutes, first when the Cameron Jerome headed a difficult chance straight at Adrian before Sebastian Bassong had to be alert to block Sakho's effort.
The returning Kouyate failed to capitalise on a good opportunity shortly afterwards when he headed Dimitri Payet's whipped free kick straight at John Ruddy from seven yards out as the hosts threatened again, but they gifted the lead to Alex Neil's side after nine minutes.
Hammers captain Mark Noble was far too casual in rolling a pass across the defence, and Liam Brady capitalised by intercepting and keeping his cool to slide a low finish under Adrian for his first goal for the club.
Norwich pressed for a second as Jonny Howson blazed over the bar from a good position, and Jerome should have doubled the lead when he could only fire into the side-netting with the Hammers' backline waiting for an offside flag.
The Canaries were made to pay for their failure to find a second after 33 minutes when Sakho finished off a move that he started himself, slotting home his fifth goal of the season from close range after Payet had picked out the striker with a return pass.
The equaliser marked a change in the run of play as the hosts dominated the final stages of the first period, and they had chances to go ahead firstly through Manuel Lanzini's well-struck free kick and then when Sakho failed to capitalise on Ruddy's error.
Adrian's fine save kept out Howson's 20-yarder shortly after the restart and Ruddy stopped Sakho from doubling his tally with a close-range header as both sides sought a winner in the second half, before Payet's skill carved out a chance for himself only to find Ruddy equal to the low effort.
Jerome's last action of the match before being substituted was to produce a reflex stop from Adrian with a stinging drive and Brady's low free kick was turned round the post as Norwich looked the more likely late on, and the visitors thought that they had won it with six minutes remaining.
Substitute Nathan Redmond's corner was initially cleared but when Wes Hoolahan gave him the ball back out wide, the winger cut inside Noble and curled a fine strike into the far corner through the crowd to stun the home supporters.
However, Ruddy could only half-clear Payet's free kick and Kouyate stabbed home in the third minute of injury time to deny the Canaries a win.