Arsenal had representatives present at Porto's game against Benfica to run the rule over Jackson Martinez, according to the Portuguese press.
The 27-year-old has attracted the interest of a number of clubs following his fine form in the Portuguese league, scoring 38 goals in 45 starts since joining from Chiapas.
Chelsea were rumoured to be strongly interested in Martinez but following the season-ending injury to Theo Walcott, Arsene Wenger has stepped up his interest in the Colombian hit man.
Wenger sent his European scout to the Estadio de Luge to watch Porto's title clash against Benfica, which they disappointingly lost 2-0.
Arsenal are thought to be keen to bring in a striker this month having been overly reliant of Olivier Giroud so far this season.
The French striker has started more games than any other outfield player for Arsenal this season and, coupled with Walcott's injury, Wenger has been left short of options up front.
Nicklas Bendtner is still thought to be three weeks away from a return to action while Lukas Podolski is working his way back to match fitness following a serious hamstring tear.
Wenger has been linked with a move for a number of strikers including Alvaro Morata and Diego Costa. However, no officials bids are thought to have been made.
A January deal for Martinez also looks unlikely due to his €40m release clause and the fact that he is cup-tied from European competitions.
But Martinez has reportedly made it clear to Porto officials that he will not sign a new contract, providing hope that Arsenal will be able to sign him for less than his steep release clause.