The Swans' unbeaten Premier League record at St James' Park ended following a 3-0 defeat to Newcastle United.
Jamaal Lascelles headed the hosts ahead with five minutes left of the first half, while the Swans wasted a string of chances after the break.
And they were made to pay for that as Moussa Sissoko doubled the lead in the 82nd minute before Andros Townsend slotted home in added-on time.
This defeat leaves the Swans ten points ahead of third-bottom Sunderland, who have a game in hand, with Francesco Guidolin's side slipping to 15th in the table.
The Swans remained unchanged as Francesco Guidolin kept faith with the same XI that claimed a first Premier League win over the Blues at the Liberty, with the only squad change seeing Leon Britton named on the bench as Ki Sung-Yueng made way.
St James' Park had proved a happy hunting ground for the Swans, having won three and drawn one of their four Premier League matches at the north east venue.
Former Swans midfielder Jonjo Shelvey, who moved to Newcastle in January, was included among the home side's substitutes.
Manager Rafael Benitez was without injured trio Daryl Janmaat, Fabricio Coloccini and Steven Taylor though Jack Colback returned from suspension.
NEWCASTLE UNITED: Karl Darlow, Paul Dummett, Jack Colback, Georginio Wijnaldum (Ayoze Perez, 73), Moussa Sissoko, Vurnon Anita, Papiss Cisse (Alexsandar Mitrovic, 80), Jamaal Lascelles, Chencel Mbemba, Cheick Tiote (Jonjo Shelvey, 66), Andros Townsend.
SUBS: Freddie Woodman, Siem De Jong, Gabriel Obertan, Rolando Aarons.
SWANS: Lukasz Fabianski, Angel Rangel, Federico Fernandez, Ashley Williams (capt), Neil Taylor, Jack Cork, Leroy Fer (Modou Barrow, 57), Gylfi Sigurdsson, Jefferson Montero, Andre Ayew (Bafe Gomis, 71), Alberto Paloschi (Wayne Routledge, 83).
SUBS: Kristoffer Nordfeldt, Kyle Naughton, Jordi Amat, Leon Britton.
Both teams took a while to settle into the game, with few clear cut chances created early on.
Jack Cork fired a 25-yard effort over the crossbar while, at the other end, Jack Colback scuffed an effort straight at Lukasz Fabianski after latching onto Papiss Cisse's flick on.
Another half chance saw Alberto Paloschi's cross strike Gylfi Sigurdsson and into the hands of keeper Karl Darlow, who was making his home debut.
Andros Townsend then cut in from his right flank before firing low towards the bottom corner, but Fabianski collected cleanly.
With five minutes left of the half, Newcastle got their goal.
Jamaal Lascelles rose highest to reach Townsend's corner and he nodded home.
HALF-TIME: Newcastle 1 Swans 0
The game was far more open in the second period, with the Swans creating far more opportunities.
Angel Rangel headed wide from a bouncing cross delivered by Neil Taylor, while Paloschi nodded Jefferson Montero's cross just past the far post.
The Swans went close to finding an equaliser with 20 points to go as a headed clearance dropped to Ashley Williams, but his sidefooted effort glided just wide.
The chances kept coming as the Swans looked the more likely to get the next goal, and Montero wasted a glorious opportunity when he was put in by sub Bafe Gomis.
The winger, though, scuffed his effort wide while under pressure from keeper Darlow.
Gomis was the next to scupper a chance as he couldn't hit the target, and the Swans were made to pay for their wasted chances.
Moussa Sissoko doubled the lead as he hammered home from close range following another corner as the home fans erupted.
And they were on their feet again in stoppage time as Townsend slotted past Fabianski to finish off a miserable day for the Swans