NEW YORK — Shares of AmerisourceBergen soared Tuesday on reports that Walgreens is pursuing a complete takeover of the huge drug distributor. The Wall Street Journal reported late Monday that Walgreens Boots Alliance Inc. reached out to AmerisourceBergen Corp. about a potential deal several weeks ago. The paper, citing anonymous sources, said no offer is on the table. Walgreens already owns about 26 percent of the company, according to data provider FactSet. AmerisourceBergen Corp. jumped more than 8 percent, to $96.88, while broader indexes slipped in late morning trading.