England had taken a 1-0 lead in the 21st minute on a header by Fara Williams, who took a cross from Karen Carney and put the ball over the head of Mexico's 16-year-old goalkeeper, Cecilia Santiago.
Ocampo, however, scored the equalizer on a fantastic shot in the 33rd minute.
On the play, Dinora Garza laid a ball off to Ocampo, who took a touch and then scorched a shot into the upper-left corner of the net from 30 yards out, leaving England goalie Karen Bardsley with no chance.
Mexico will next play Japan Friday in Group B play while England will take on New Zealand the same day.
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