ROME (Reuters) - Italy's antitrust agency (AGCM) said on Monday it had opened an investigation into Edison's sale of its gas storage unit to gas grid operator Snam.

AGCM said in its weekly bulletin it would probe whether the deal could significantly restrict competition "by strengthening Snam's dominant position in the gas storage market."

When the two companies announced in July the deal for the three gas storage sites, they said it was worth up to 630 million euros ($656.52 million).

($1 = 0.9596 euros)