Leading article: Heat on The Sun can only intensify

After the exposure of the Milly Dowler affair, it seemed as if matters had become as bad as they could for Rupert Murdoch's media empire. Public fury in Britain about the hacking of the murdered girl's mobile phone was on such an epic scale that Mr Murdoch took what then seemed the drastic action of closing the offending newspaper, the News of the World.

But now even that shocking development is starting to lose its significance in the News International saga, as police take ever more reporters at The Sun in for questioning under the terms of Operation Elveden, which is investigating alleged bribes by journalists paid not only to police but also to prison staff and Ministry of Defence officials.

The danger for News International's remaining UK media stable is growing by the day. Operation Elveden could turn out to be far more toxic for the future of the company even than Operation Weeting, which is the inquiry into phone-hacking allegations.

As the Management and Standards Committee, the investigative body set up by News International's parent company, News Corporation, continues ploughing through millions of journalists' emails, feeding information to Scotland Yard, the prospect grows of the cancer originally confined to the NOTW spreading across the Atlantic and from one part of Mr Murdoch's media empire to another.

Where this leaves The Sun remains to be seen. But what seemed unthinkable until a day or two ago – Mr Murdoch's enforced abandonment of this flagship newspaper – cannot be discounted. The sale or closure of The Sun is, however, a different matter to the closure of the NOTW. Some believed Mr Murdoch had plans to rebrand the NOTW in any case, as The Sun's Sunday arm.

It is less easy to see how it would fit Mr Murdoch's strategy to lose a daily whose estimated £650m annual profit sustains News International's two other newspapers, The Times and Sunday Times. The loss of The Sun would also affect the sale price of News International. It is too early to predict whether it will come to this, though if it did, it would have far-reaching implications for the whole UK media.