MANKATO, Minn. -- At least part of the Percy Harvin mystery we discussed Monday has been solved. Minnesota Vikings coach Brad Childress confirmed Tuesday that Harvin has been suffering from migraine headaches during a nine-day absence from training camp that originally began with the death of his grandmother.

Childress said Harvin has been convalescing at his home near the Vikings' permanent training facility in Eden Prairie, Minn. It's still not clear the extent to which the migraines are responsible for his extended absence. But the revelation at least helps explain why Harvin has missed much more time than NFL players typically take after a death in the family.

"He's had some [migraines]," Childress said. "He's had some. God willing, he's going to work through this."

Harvin has suffered from migraines throughout his life, and they caused him to miss one regular-season game last season. The episodes can confine him to bed for up to a week at a time. The Vikings have sent him to specialists at the Mayo Clinic and elsewhere but to this point have been unable to curb their frequency.

"It's ongoing," Childress said. "The only thing that would be wrong is if we quit trying to find things and throw our hands up in the air. It's kind of an inexact science."

As of Tuesday morning, the Vikings still had no idea when Harvin would rejoin the team. With training camp scheduled to break Thursday, you wonder if Harvin will return to Mankato at all. If that's the case, he will miss more than two weeks of practice before getting back on the field. Stay tuned.