The 6ft 5in stopper, currently on the books at Serie A side Torino, watched United’s 1-1 draw with Fulham from the stands.
Jansson, 25, who moved to Torino from Malmo in July 2014, has been capped seven times by Sweden.
Jansson, who worked with United assistant boss Pep Clotet at Malmo earlier in his career, moved to Italy and Torino in 2014 but has seen his opportunities limited in Serie A.
Despite that, he was named in Sweden’s Euro 2016 squad and is widely expected to become a regular for his national team under new coach Janne Andersson.
United head coach Garry Monk, who dropped captain Sol Bamba last night after two straight league defeats, has been on the look-out for another central defender throughout the summer and is hoping to see a deal for Jansson completed before Saturday’s derby at Sheffield Wednesday.
Hull City are set to table a £9m bid for Lorient striker Benjamin Moukandjo as they seek to make a major transfer breakthrough after a difficult summer.
The 27-year-old Cameroon international, at home on both wings or as a central forward, impressed Tigers scouts in scoring twice in Lorient’s 3-2 defeat at Caen last weekend.
Moukandjo, who scored 13 goals for Lorient last season, has a year left on his deal in France and is also reportedly on the radar of West Brom, Sunderland and Swansea.
The Tigers are also endeavouring to add Hungary forward Nemanja Nikolic to further supplement their diminished striking options.
The Legia Warsaw forward has been linked with a £2.5m switch with contact made with officials at the Polish club, although any move will have to wait until after Legia’s Champions League commitments - with the return leg of their tie with Irish outfit Dundalk taking place next Tuesday.
Nikolic fired an outstanding 36 goals in 55 games last season.
Atletico Madrid midfielder Oliver Torres has snubbed the advances of Middlesbrough in favour of a loan move to Porto.
Torres, 21, spent the season before last on loan at the Portuguese outfit before being recalled by Diego Simeone and featuring 33 times in all competitions for Atletico last term.
Manchester United officials are hoping to persuade Brazilian midfielder Andreas Pereira, linked with Boro last week, to agree to a loan move to a Premier League club - putting the Teessiders on alert.
Pereira was told after United’s pre-season tour of China that he didn’t feature in Jose Mourinho’s first team plans this season, leading to the player’s representatives reportedly looking into the possibility of a permanent move to PSV Eindhoven.
But United do not want to lose the 20-year-old to a European club and want him to stay in the top-flight.