As 48-Hour Mark Looms, BP Watches

As this afternoon marks the critical 48-hour point since BP plugged its Macondo well, engineers tensely monitor pressure readings and underwater images from their massive cap and try to decipher them. With pressure at the wellhead rising ever so slowly—yet rising nonetheless—BP hopes to have more definitive data that its cap is working...and that leaks haven't sprung up elsewhere.

One expert warns the AP that the lower-than-expected readings could signal an impending underground blowout, while another says if the pressure is "rising slowly, that means the pipe's integrity's still there." President Obama cautioned the public "not to get too far ahead of ourselves," warning of the danger of new leaks "that could be even more catastrophic." (More Gulf oil spill stories.)