I have recently run into CPU overages on my site due

I have recently run into CPU overages on my site due to Multiple processes of /home/cohortco/public_html/wp-admin/admin-ajax.php running.

What plugin could be responsible for this kind of CPU load?

Details of CPU usage:
-> CPU usage for the account is 47 times the server average
-> The limitation mention was reached at 9am EDT this morning, 9/24/13. Below are the processes that were running on your account at this time.
-> Multiple processes of /home/cohortco/public_html/wp-admin/admin-ajax.php running from 9-10am EDT.