At Galeras volcano in Colombia, it was carried out several microgravity campaings. Attached you can find Gerhard Jentzsch paper:

Gravity changes and internal processes – some results obtained from observations at three volcanoes.

At the foot around the Galeras volcano gravity is constant, the gravity change is around zero within the error bars. Along the main profile leading to the top the gravity increase reaches a maximum of 800...900 nms-² at ca. 3 km from the top, further decreasing to a gravity increase of about 200 nms-² near the top over a time span of half a year (second campaign). This is confirmed by the third campaign after one more year. Four additional short profiles around Galeras, running from the foot of Galeras volcano in direction to the top, show a similar tendency of gravity increase, including the phenomenon of a maximum and decline with decreasing distance from the top. Although the gravity change at these shorter profiles is not significant it is confirmed by the results of the third campaign as well as by the fact, that all profiles around Galeras volcano show the same trend.