London - England were left with increasing concerns at prop after Beno Obano was summoned into their training squad on Thursday ahead of this weekend's Six Nations clash with Ireland at Twickenham.
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Doubts over the fitness of either Joe Marler or Ellis Genge have seen Obano recalled from club side Bath after he was dropped from an initial 33-man training squad on Wednesday.
Earlier this week experienced front-row forward Mako Vunipola was ruled out of Sunday's match, England's first home fixture this Six Nations, for family reasons that have seen him return to Tonga.
Jones refused to specify which one of Marler or George was doubtful for Sunday's match.
But if either of the pair are ruled out that would leave Obano in line to make a Test debut against an Ireland side chasing a Triple Crown after wins over Scotland and Wales in the opening two rounds of this season's Six Nations.
"Beno's on the freight train, just in as a bit of cover," Jones told reporters on Thursday.
"As I said we've got a few niggles so we just needed an extra prop in there," added the Australian, who is set to name his team on Friday.
World Cup finalists England started the Six Nations with a loss away to France before reviving their title hopes with a 13-6 Calcutta Cup win over Scotland at Murrayfield.