* Di Maria ends nearly two hours of deadlock
* Swiss almost equalise in enthralling finale
* Cameroon open match-fixing investigation
* Dutch midfielder De Jong likely out of tournament
By Brian Homewood
BRASILIA, July 1 (Reuters) - Argentina took 118 minutes to break down stubborn Switzerland then survived an extraordinary, heart-stopping finale before reaching the World Cup quarter-finals after a dramatic 1-0 win on Tuesday.
With penalties looming, Angel Di Maria stroked the ball home from the edge of penalty area to put the finishing touch to a trademark Lionel Messi run, sparking wild celebrations among the South Americans and their fans in Sao Paulo.
There was still time for Swiss substitute Blerim Dzemaili to head the ball against the post from point-blank range and his team mate Xherdan Shaqiri to send a free kick straight into the Argentina wall amid unbearable tension.
"Football is brutal, brutal, brutal. Unfortunately, we didn't quite have enough strength at the end to get through extra time," said Switzerland's assistant coach Michel Pont.
Argentina face either Belgium or the United States, who were meeting in the final second round clash later on Tuesday (2000 GMT), in their quarter-final in Brasilia on Saturday (1600 GMT).
Off the field, Cameroon's football federation (FECAFOOT) said they would investigate claims that seven of their players were involved in match-fixing at the World Cup, centred on the 4-0 defeat by Croatia when Alex Song sent off in the first half.
"Recent allegations of fraud around Cameroon's three 2014 World Cup games, especially Cameroon v Croatia, as well the existence of "seven bad apples (in our national team)" do not reflect the values and principles promoted by our administration," FECAFOOT said in a statement.
The allegations against Cameroon came from convicted fraudster Wilson Raj Perumal, who had accurately forecast the result and the fact that a player would be sent off during a discussion with German magazine Der Spiegel.
The Netherlands, who face Costa Rica in a quarter-final on Saturday, suffered a blow when defensive midfielder Nigel de Jong was effectively ruled out of the rest of the World Cup with a groin injury.
The Dutch football association (KNVB) said in a statement that De Jong would be sidelined for two to four weeks, exceeding the duration of the tournament which ends on July 13.
Nigeria coach Stephen Keshi was reported to have quit his post, one day after their last 16 exit to France, but this was denied by the country's football federation.
Argentina became the seventh team to reach the quarter-finals, all of them winners of their first round groups.
Like Brazil, Costa Rica, the Netherlands, Germany and France before them, they had to suffer much more than in the group stage before finally booking their place.
Although Argentina dominated the match, their attacks lacked variety and Switzerland, brilliantly marshalled by veteran coach Ottmar Hitzfeld in his last game in charge, defended superbly.
Hitzfeld is now retiring following a career in which he has won seven Bundesliga and two Champions League titles.
The Swiss broke forward when they had a chance and created several chances, with Josip Drmic wasting the best when he chipped the ball into Sergio Romero's arms from an excellent position.
"Yesterday Germany, Holland the day before. Nothing's easy, it's all hard work. Football has evolved today and everything is very level," said Argentina midfielder Javier Mascherano, referring to narrow victories by the Germans and Dutch.
"We always tried to play, we just made one mistake in the first half that allowed a one-on-one with 'Chiquito' Romero," added Di Maria. (Additional reporting by Mark Gleeson in Salvador; Editing by Ken Ferris)