By MATTHEW PERRONE
AP Health Writer
WASHINGTON (AP) — Many questions remain about the shuttered Abbott baby formula plant at the center of a nationwide shortage. Although U.S. officials have a deal with Abbott to restart production, it’s not yet clear how soon the site will be up and running. Even bigger questions remain unanswered, including what caused the contamination. The Food and Drug Administration also faces scrutiny over whether it could have alleviated the current shortage by stepping in sooner. The FDA hasn’t released a final ruling on the problems at the plant or an accounting of the steps it took ahead of the shutdown.