The merger would likely be structured as "an all-stock, at-market transaction, based upon the unaffected trading prices of the two companies' stock prior to media reports of a possible merger," ProLogis said in its statement. ProLogis said the talks may not necessarily result in a definitive agreement, and would not commit to a timeframe in which such an agreement would take place. "ProLogis and AMB have issued press releases in response to media reports and intend to make no further comment regarding their discussions or negotiations unless and until a definitive agreement is reached or discussions are terminated," said both companies in their respective statements. ProLogis shares closed 8% higher at $15.87. Nearly 33 million shares changed hands, more than six times the issue's trailing three-month daily average volume of 5.7 million.